In order to grind the surface of metallic materials such as iron materials, aluminum materials, or copper materials, grinding tools have been conventionally used. In grinding with the use of the conventional grinding tool, by moving the grinding tool with the use of a manually or numerically controlled (NC: Numerical Control) processing machine, grinding of the surface having a planar shape or a shape approximate to a plane could be performed without any hindrance. However, in case of grinding a curved surface or a nonuniform surface, grinding in a state that a positional relationship between a grinding stone tip provided at a leading end of the grinding tool and the surface of the metallic materials is uniform is difficult, so it was difficult to grind the surface of the metallic materials by a uniform grinding force.
As a result, under-grinding portions or over-grinding portions are generated on the surface of the metallic materials after grinding, and depending on the time, some flaws were generated on the surface of the metallic materials. Further, overload may be applied at the time of grinding, a grinding shaft may be broken, or abnormal wear may be generated on the grinding stone tip, so the development of a grinding tool without creating these problems has been conventionally expected.
Based on the above-described background, various studies have been conventionally carried out to realize a desired grinding tool. The invention proposed based on the knowledge that a rotating tool containing 50% by volume or more of inorganic continuous fibers does not require special consideration of the angle at which it abuts on a work-piece and has an excellent sharpness over all directions is the invention described in Patent Document 1. In the Patent Document 1, as an example of the rotating tool suitable for grinding, a rotating tool consisting of a rotating tip which rotates, and a turning shaft for turning the rotating tip is disclosed.
This rotating tool uses fibers of high hardness instead of a grinding stone, and is formed densely using a thermosetting resin as a binder so as to have no holes. As thus configured, the thermosetting resin of the matrix is worn away slightly earlier than the inorganic continuous fibers at the time of cutting (grinding), so the inorganic continuous fibers form a brush-like face protruded slightly from the surface of the matrix. Since this brush-like inorganic continuous fibers become cutting elements, special consideration of the angle at which it abuts on the work-piece is not necessary, and therefore this rotating tool has an excellent sharpness over all directions.
However, in Patent Document 1, only a disk-shaped rotating tool for cutting steel plates is exemplified as embodiments. Further, there is no even suggestion in addition to description of the mechanism thereof, so it is unclear whether the rotating tool described in Patent Document 1 has an excellent grinding force over all directions or not.
Moreover, Patent Document 2 proposes a grinding tool having a grinding stone tip consisting of an inorganic continuous fiber reinforced resin body in which the leading ends of a plurality of inorganic continuous fibers reach a processing surface, and a grinding stone supporting member to which the grinding stone tip is coupled. This grinding tool is characterized in that the grinding stone tip supporting member is elastically deformable in the direction orthogonal to the length direction of the grinding stone tip supporting member.
However, in the grinding tool described in Patent Document 2, if the grinding stone tip supporting member is elastically deformed in the direction orthogonal to the length direction of the grinding stone tip supporting member, the positional relationship (distance) between the grinding stone tip provided at a leading end of the grinding tool and the surface of metallic materials is changed. Therefore, it is considered that the processing force applied to the grinding stone tip will be similarly changed, and that the shape of the processing surface of the metallic materials, the wear volume of the grinding stone tip, or the like will be affected. As a result, it is considered that a stable processing by a uniform grinding force cannot be performed.